1. Field of the Invention
This invention relates to improvements in the technique of using an image formation apparatus while dividing it into a main body and a process kit removably mountable with respect to the main body.
2. Description of the Prior Art
An electrophotographic copying apparatus is taken as an example of the image formation apparatus. In such a copying apparatus, there are sometimes disposed around a photosensitive medium magnetic rollers which are magnetic field generating means. For example, in the developing device for developing the latent image on the photosensitive medium, such magnetic roller is used to stir toner or convey toner to the latent image. On the other hand, in the cleaning device for removing any toner remaining on the photosensitive medium, such magnetic roller is used to convey the collected toner.
These magnetic rollers are constructed by magnetizing magnetic members or by embedding a plurality of long magnets or adhesively securing them together. Thus, the magnetic rollers themselves are expensive and heavy parts, but the durability thereof can be made semipermanent.
It is known to use an image formation apparatus while dividing it into a main body and a process kit removably mountable with respect to the main body. Examples of such process kit include a photosensitive medium which may become exhausted or deteriorated with formation of images, a discharger including corona wire, a developing device and a cleaning device or a combination thereof, all of these being made removably mountable with respect to the main body. Such process kit may become exhausted or deteriorated with formation of images and there would occur to mind a method of use comprising replacing it with a new kit. As another example of use, there would occur to mind a method of use comprising preparing a plurality of process kits corresponding to the differences in color of toner or preparing a kit including a developing device exclusively for half-tone and a kit including a developing device exclusively for characters and inserting into the main body a kit suited for the purpose of use.
Where a developing device and a cleaning device exist on the process kit side which is removably mountable with respect to the main body as described above, it would occur to mind to provide the magnetic field generating means such as magnet rollers integrally with the kit for the movement or conveyance of toner.
Generally, however, the magnetic field generating means are not only heavy but also suffer from no extreme consumption or deterioration. Accordingly, providing the magnetic field generating means in each process kit makes the kit heavy and in addition, it would be very uneconomical to discard the kit in accordance with the durability limit of the kit.